Field of the Invention
The invention relates to a control unit for a passenger restraint system and/or passenger protection system for vehicles, for instance, for an air bag and/or belt tensioner and/or collapsible roll bar, including:
one or more acceleration or deceleration sensors, such as a sensor having a piezoresistive sensor element, which generate an electronic, analog output signal, and/or an originally analog sensor output signal digitized by an analog/digital converter, corresponding to the acceleration or deceleration acting upon the applicable installation site in the vehicle, so that the course of the sensor output signal over time corresponds to the applicable course of the accelerations or decelerations,
one or more evaluation circuits that evaluate the sensor output signal or signals, above all with a view to whether or not threshold values are exceeded, and
a tripping circuit, which trips one or more passengerprotection components of the system if one or more threshold values are exceeded, wherein
the sensor output signals are each subjected to a plurality of different evaluations, in that the sensor output signals are supplied to an evaluation circuit of complex operation or to a plurality of evaluation circuits operating differently from one another, each of which evaluate the temporal course by different criteria and thus evaluate them by a plurality of differently defined threshold values,
at least one of these evaluation circuits is constructed and operated in such a way that, from typical characteristics of the temporal course supplied to it and from the definition of the threshold value assigned to it, it distinguishes at least two different types of accidents from one another, for instance head-on and oblique, broadside and/or rear-end, to which types differently defined threshold values for the severity of the accident are assigned,
at least one of these evaluation circuits is constructed and operated in such a way that from typical characteristics of the temporal course supplied to it and from the definition or definitions assigned individually to it for the threshold value or values, it ascertains the severity of the type of accident individually assigned to it,
outputs of the evaluation circuit or circuits are connected to inputs of at least one logically linking linkage element, which links the applicable evaluation outcomes and which supplies its linkage outcome from its output to the tripping circuit, and
the logical linking function of the linkage element or elements is selected in such a way that the system is tripped only if the evaluations by the various criteria showed both a defined type of accident from a plurality of defined accident types, and that the threshold value or values that have been specifically assigned to the applicable type of accident have been exceeded.
Such a device is known from German Published, Non-Prosecuted Application DE-A 2 123 359, corresponding to U.S. Pat. No. 3,762,495.
In order to improve or optimize the reliability of the control unit, namely to increase the certainty that mistaken tripping of the system will be avoided, the known control unit already has a plurality of circuits, which use various threshold values based on characteristic features of the sensor output signal to ascertain more or less accurately which type of accident, such as head-on collision or broadside crash, is involved, and how critically the decelerations or accelerations being measured are to be evaluated. Above all, in the initial phase of the accident, which is definitive for the evaluation, the courses of the sensor output signals over time differ more or less markedly from one another, so that they allow a conclusion to be drawn more or less not only as to the type of accident but also as to the incipient severity of the accident, even in the initial phase.